Kilometres per hour
Kilometre per hour (American spelling: kilometer per hour) is a unit of both speed (scalar) and velocity (vector). The correct SI symbol is km/h or km·h−1, although the unit is sometimes written colloquially as kph, kmph, or km/hr. None of these corruptions is correct under the rules of SI in reference to correct style when using symbols. It is often spoken and sometimes written as klicks or kays in slang usage.
By definition, an object travelling at a speed of 1 km/h for an hour would move 1 kilometre.
- 3.6 km/h ≡ 1 m·s−1, the SI derived unit of speed, metre per second
- 1 km/h ≈ 0.27778 m/s
- 1 km/h ≈ 0.62137 mph ≈ 0.91134 foot per second
Examples of speeds in km/h
| 5 km/h | Walking speed |
| 20 km/h | Easy bicycling speed |
| 36 km/h | Top speed of a running human. (100 m in 10 seconds) |
| 50 km/h | Residential speed limit Top speed of a running cat, or dog |
| 80–90 km/h | Speed limit on a major road Top speed of an antelope |
| 110–120 km/h | Highway or motorway speed Top speed of a cheetah |
| 300 km/h | High-speed train |
| 1,000 km/h | Airliner cruising speed |
| 1,200 km/h | The approximate speed of sound (at sea level) |
| 1,228 km/h | Current world land speed record |
| 26,000 km/h | Re-entry speed of the space shuttle |
| 40,320 km/h | Earth's escape velocity |
| 1,079,252,848.8 km/h | Speed of light (exact) |